Armed for the first time with data that rates the effectiveness of more than 12,000 math and reading teachers, parents yesterday said they’ll now take action to steer their kids clear of bad apples.

At PS 89 in The Bronx — which had the highest number of teachers who were rated poorly in 2010 — several parents returning to school yesterday after last week’s mid-winter recess said they plan to pull their kids out.

Forty-three percent of the Bronxdale school’s teachers were rated below average or worse, while just 7 percent were above average or better, according to the city’s numbers.

“I am concerned. I am not happy with the school,” said Carmen Vega, a 32-year-old dental receptionist with a daughter in first grade. “I’m going to change her school next year. She won’t be here. This school needs a hell of a lot of help.”

Others said that the issues went beyond subpar teaching to other factors, like bullying and safety, but that the data confirmed their concerns about low reading scores.

“I’m keeping him here, but I probably will eventually get him out,” Janet Rosado said of her son, also a first-grader.

Principal Ralph Martinez, who took over the C-rated school in September 2010 — the year after the rankings of fourth- through eighth-grade teachers were calculated — was among a host of educators and parents who dismissed the data as inaccurate.

The ratings, also known as teacher data reports, rank teachers on a scale of zero to 99 based on comparisons to their peers with similar levels of experience.

Yet individual percentile rankings had margins of error as high as 75 in math and 87 in English — rendering them all but meaningless in the eyes of critics.

“I have a group of amazing teachers at our school. I don’t think [the data] is completely reflective of what PS 89 currently is,” said Martinez, who has introduced new technology, uniforms and educational supports.

“Have we been able to meet every parent’s needs? Not all 100 percent,” he added. “But we’re working on it.”

Overall, reactions to the reports — which attempt to measure a teacher’s contribution to their students’ gains on state math and reading tests, while excluding dozens of variables such as poverty and class size — varied widely yesterday.

At PS 321 in Park Slope — which is universally hailed as a Brooklyn gem but where 18 percent of the teachers scored low marks in 2010 — many parents condemned the city for reducing teacher effectiveness to a number.

“Parents are just horrified that this information was made public. It’s just awful,” said Lori Chajet, 40, whose daughter, Sonia, is in third grade. “We are beyond thrilled with the teachers here. Whoever designed these [reports] should know that they hold no value to us whatsoever.”

At PS 32 on Staten Island, however, some parents said the data confirmed their suspicions that teacher quality differed from classroom to classroom.

Half the teachers at the Great Kills school were rated average, and the rest were split between above average and below average.

“[It’s] not surprising at all,” said Monique Alparrawe, who has already pulled one child out of the school because of concerns about the teaching — and plans to pull another.

“My son is definitely not coming back here next year,” she said. “I don’t like half the teachers here.”